Low-entropy states: Persuading Maxwell’s Demon to order atoms

A new technique allows sorting atoms one by one to form ordered patterns in a periodic lattice with angstrom precision

For German speakers, you can hear the interview with Forschung aktuell of Deutschlandfunk – Sortiergerät für Atome: Forscher präparieren Quantenregister im Rekordtempo (broadcast on March 9th)

Creating low-entropy states of neutral matter is one of the outstanding problems in the field of quantum optics. These states are an indispensable cornerstone of future applications in quantum information science, ranging from quantum simulations to quantum information processing. In Robens et al. Phys. Rev. Lett. 118, 065302 (2017), we demonstrate a new technique using two periodic optical potentials—the storage and shift register—to sort neutral atoms one by one into predefined patterns. Hence, our original experimental scheme acts akin to a Maxwell daemon preparing states with virtually zero entropy. Behind this scheme stands a novel idea for the fast, high-precision synthesis of polarization states of light—hence the name of polarization-synthesized optical lattices. Using the storage and shift register enables a novel sorting algorithm of logarithmic complexity, which holds promise to sort even a thousand atoms into a predefined target pattern with angstrom precision in a second. In our manuscript, we give a proof-of-concept demonstration by generating low entropy states with four atoms (see figure).